SAND EXTRUDITES: A NEW STYLE OF

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SAND EXTRUDITES A NEW STYLE OF STRATIGRAPHIC
TRAP THEIR SIGNIFICANCE IN BASIN ANALYSIS
ANDREW HURST University Aberdeen, Dept. Geology
Petroleum Geology MADS HUUSE, MARIO VIGORITO,
DAVIDE DURANTI, JOE CARTWRIGHT
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A SAND EXTRUDITE
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SAND EXTRUDITES

• HOW ARE THEY RECOGNISED
• ARE THEY SIGNIFICANT RESERVOIRS
• HOW DO THEY FORM / ROLE IN BASIN EVOLUTION
• PROSPECTIVITY

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SAND EXTRUDITES RECOGNITION
650m
TIME SLICE EOCENE, MORAY FIRTH
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SAND EXTRUDITES RECOGNITION
Outer Moray Firth, Eocene
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SAND EXTRUDITES RECOGNITION

• BEDDING CONCORDANT
• LOW RELIEF
• LATERALLY DISCONTINUOUS ??
• FED BY SAND INJECTITES

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SAND EXTRUDITES RECOGNITION
VOLUND FIELD PRE-DISCOVERY
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RECOGNITION NOT SAND EXTRUDITES
24/9-7B
Seismic (near offset amplitude data) through
wells N24/9-7B, 24/9-7 and 24/9-6 pink horizon
is top Balder Formation, red and blue horizons
are top and base of injection complex.
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RECOGNITION NOT SAND EXTRUDITES
VOLUND FIELD, MARATHON/ LUNDIN
courtesy of Ewa Szarawarska
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ARE THEY SIGNIFICANT RESERVOIRS
THE ABSENCE OF MIND MODELS !!
USE OF OUTCROP ANALOGUES TO CREATE NEW MODELS FOR
STRATIGRAPHIC TRAPS
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ARE THEY SIGNIFICANT RESERVOIRS
MIOCENE SAND EXTRUDITES, N MONTEREY
BAY METRE-SCALE SAND EXTRUDITES
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ARE THEY SIGNIFICANT RESERVOIRS
RED, WHITE BLUE BEACH, SANTA CRUZ
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TAR-STAINED, BEDDED SANDSTONE, 1.5-3.5 M
THICK RED, WHITE BLUE BEACH, SANTA CRUZ
ARE THEY SIGNIFICANT RESERVOIRS
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IDENITIFICATION OF RESERVOIR-SCALE FEATURES
HIGHLY DISRUPTED BASE, LOCALLY CONCORDANT TAR
SATURATED FED BY HIGH- LOW-ANGLE DYKES -
DIVERSE INTERNAL STRUCTURES BIOSILICEOUS UPPER
UNIT WITH CONCORDANT TOP
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SUSTAINED FLOW _at_ ca. 0.4-0.6 ms-1 FROM
WNW COINCIDENT WITH HIGHLY DISRUPTED SEAFLOOR
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ARE THEY SIGNIFICANT RESERVOIRS
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• VENT DYKE IS PART OF A LINNEAR FRACTURE
• LOW-ANGLE LAMINAE/THIN BEDS PREDOMINATE
• BURROWS COMMON NEAR TOP

ASSOCIATION WITH SAND INJECTITES
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LOCALLY BRECCIATED VENT AREA
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ARE THEY SIGNIFICANT RESERVOIRS MULTIPLE
EXTRUSIONS
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ARE THEY SIGNIFICANT RESERVOIRS AREAL
EXTENT Panoche Giant Injection Complex, U.
Cret-Paleocene, Great Valley, CA
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ARE THEY SIGNIFICANT RESERVOIRS AREAL
EXTENT Panoche Giant Injection Complex, U.
Cret-Paleocene, Great Valley, CA
Cretaceous Marine Deposits
PGIC
Palaeocene-Miocene Marine Deposits
500 km2 of outcrop extrudite up to 15 m thick
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ARE THEY SIGNIFICANT RESERVOIRS SUMMARY IN
DEEP-WATER CLASTIC SYSTEMS
BEDDING CONCORDANT LATERALLY EXTENSIVE MAY BE
STACKED UP TO 15 m THICK FED BY DYKES
ASSOCIATION WITH INJECTITES OVERALL FU BUT EVEN
GRAIN-SIZE DISTRIBUTION Internal
Structures LOW-ANGLE BEDDING (RADIAL CURRENT
FLOW), BURROWED, SOME X-BEDDING, SLUMPING,
MUD INTRACLASTS
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SUDDEN RELEASE OF OVERPRESSURE AT DEPTH SEAL
FAILURE SAND FLUIDISATION PRESSURE
EQUILIBRATION LARGE EXTRUDITES REQUUIRE LARGE
AQUIFERS MINS/DAYS
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HOW DO THEY FORM ROLE IN BASIN EVOLUTION
A MODERN TERRESTRIAL EXAMPLE OF SAND
EXTRUSION FROM WATSONVILLE, CA SAN ANDREAS
FAULT ZONE
PRESERVATION POTENTIAL IS DEPENDENT
ON SEAFLOOR/SURFACE CONDITIONS NO REWORKING
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HOW DO THEY FORM BASIN EVOLUTION
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SAND EXTRUDITES PROSPECTIVITY HIGH LATERAL
CONTINUITY SEISMICALLY RESOLVABLE
PERFECT STRATIGRAPHIC TRAPS ON MIGRATION
ROUTES OCCURRENCE OF SAND INJECTITES A
PRE-REQUISITE PERIODS OF OVERPRESSURE DURING
SHALLOW BURIAL LARGE AQUIFER VOLUME - SEISMICITY
(RAPIDITY) PARENT SANDS WITHIN THE SHALLOW
SECTION FOCUS ZONES/AREAS FOR SUBSURFACE
FLOW FACIES TECTONIC SETTING INDEPENDENT
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CORRELATING CORRECTLY
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CONCLUSIONS SAND EXTRUDITES
PERFECT STRATIGRAPHIC TRAPS WIDELY DEVELOPED,
RARELY RECOGNISED UNRECOGNISED IN
CORES SIGNIFICANT VOLUMES LARGE AREA,
THIN SIGNIFICANT TIME LINES RECORD PERIODS OF
SHALLOW OVERPRESSURE AN UNTESTED PLAY CONCEPT